The approach taken by the Leicester team was to focus on mitochondrial DNA, which is inherited through the maternal line and is typically more stable and more abundant in ancient samples than nuclear DNA. Mitochondrial DNA is passed from mother to children, and each of those children passes it to their own children, so that the mitochondrial DNA of a given individual should match that of any living person who descends from the same maternal ancestor through an unbroken female line — or through a female line with only a single change in any given position.
The challenge was identifying a living person who satisfied that criterion. The maternal lineage needed to trace an unbroken female line from a woman who was an ancestor of Richard III down to the present day — a requirement spanning roughly 500 years and the complete genetic lottery of who would have children, who among those children would be daughters, and which of those daughters would have had their own children.
John Ashdown-Hill, the historian who had done the documentary research pointing to the Greyfriars site, had also conducted earlier genealogical research specifically aimed at identifying such a descendant. He traced the maternal line from Anne of York, Richard III’s sister, forward through the generations. Anne’s mitochondrial DNA would have been the same as her brother’s, inherited from their shared mother, Cecily Neville.
The research identified a living maternal-line descendant: Joy Ibsen, a Canadian woman who had died in 2008. Ashdown-Hill had managed to trace the line forward from Anne of York through Joy Ibsen and had extracted a DNA sample from her with her cooperation before her death. Joy’s mitochondrial DNA belonged to haplogroup J — a lineage that traces its origins to the Middle East tens of thousands of years ago and spread into Europe during prehistoric migrations.